As Discovery Heads Home, NASA Prepares for Landing

HOUSTON - Flightcontrollers are watching the weather for Discovery's return to Earth Monday andare planning alternate landing sites should rain storms in Florida prevent theearly-morning touchdown, mission managers said Saturday.

The shuttle undocked from the International SpaceStation (ISS) earlier today and flew around the orbital platform before headingback to Earth.

"The undocking andfly-around both went by the book," said Paul Hill, lead shuttle flightdirector for the orbiter's STS-114 mission. "We couldn't be happier withthe operational success of STS-114."

Discovery's only landingtarget Monday is NASA's Kennedy Space Center (KSC) in Cape Canaveral, Florida,where it launched spaceward on July 26. While theorbiter is slated to land at 4:46 a.m. EDT (0746 GMT) on Aug. 8, it could alsoland 5:21 a.m. EDT (0921 GMT) if weather prevents the initial attempt.

Both KSC and a contingency runway at Edwards Air Force Base inSouthern California will be on call Tuesday if needed, shuttle officials said,adding that a third airstrip in White Sands, New Mexico is also a landingoption.

Current weather predictionsat KSC call for light and variable winds, a few scattered clouds and a slightchance of rain during the predawn hours of Discovery's landing opportunities,they added.

"That's about as gooda forecast as you're going to get in Florida, but I have high hopes," saidWayne Hale, NASA's deputy shuttle program manager, during a press briefing hereat Johnson Space Center. "You don't commit untilit's time to de-orbit."

By a chance of orbitalmechanics, most of Discovery's Monday landing approach will be over water -though it will pass over parts of Central America and Cuba before reachingsouth Florida and homing in on the at the Shuttle Landing Facility runaway atKSC. That ground track poses little risk to the populations the shuttle fliesover, a new consideration for NASA since the Columbia orbiter broke apart overTexas in 2003, scattering debris across the region, shuttle officials said.

"These ground tracksare low risks in terms of public overflighthazards," Hale said. "This is a new topic for us, [and] it's not aconcern for our primary landing site at the Kennedy Space Center."

Should Discovery and itsSTS-114 crew, commanded by veteran astronaut Eileen Collins, be forced to landat Edwards Air Force Base, flight controllers have tweaked two trajectories toshift them away from passing over major population areas in the Los AngelesBasin, Hale said.

Limiting flight overpopulated areas is largely tied to whether Discovery is suffering from anyhazard concerns. This is not the case for the STS-114 flight, shuttle officialssaid, citing data from sensors inside the orbiter's wing leadingedges that confirm no impacts from micrometeorites at all thus far in the13-day mission.

"We thought thebatteries were going to run down after 36 hours," Hale said of thesensors, which were primarily designed to monitor wing impacts and temperaturesduring launch. "This vehicle is in extremely clean shape."

Discovery's STS-114 flightis NASA's first shuttle mission since the 2003 Columbia accident, which claimedthe lives of seven astronauts and destroyed their spacecraft. Investigatorslater found that a chunk of foam insulation fell from Columbia's external tankand pierced the shuttle's heat shield during launch, critically wounding theorbiter. The resulting damaged allowed hot gases to enter the orbiter's wingduring reentry and destroy the vehicle on Feb. 1, 2003.

Hale said there are about47 in-flight anomalies that shuttle engineers will have to address from theSTS-114 flight before they launch the space shuttle Atlantis on NASA's secondreturn-to-flight mission. The Sept. 22 launch target for Atlantis' STS-121spaceflight discussed Friday by NASA officials remains tenuous due to the workrequired, he added.

Discovery must be turnedaround and prepared to serve as a rescue shuttle for Atlantis' STS-121 mission,and there work still remains to prepare Atlantis itself for launch, Hale said.There is also the challenge of addressing the foam debris shedding seen during Discovery's launch,which shuttle officials have pledged to understand and fix before Atlantis orany other orbiter flies.

"I would not call thata serious launch date at this point," Hale saidof Atlantis' Sept. 22 target. "It's just a date for people to startthinking about, is there something we can do by then or not."

Meanwhile, all eyes will beon Discovery and its STS-114 crew during Monday's planned reentry, shuttleofficials said.

"I'm looking forwardto watching the crew walk off the orbiter in Florida," Hill said.

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